GEOG 432
Energy Policy

Energy Resource Types

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Energy resource types are different from types of energy. Energy resource types refer to the origin of the energy source itself, while types of energy refer to different types of potential (chemical, electrical, etc.) and kinetic (heat, sound, etc.) energy.

In this lesson, we'll look at energy resources types. As you go through the lesson, be thinking about the implications of the qualities of these energy resources on energy policy.

Generally, we can break energy into two broad categories of resources - non-renewable and renewable.

Non-renewable energy resources

These resources have formed over millions of years of geological processes, and we're using them faster than they can be naturally replenished. Examples include fossil fuels like coal, petroleum, and natural gas. We currently depend on non-renewables to meet most of our energy demands, extracting and combusting them primarily to generate electricity or develop fuels for transportation.

While we often consider nuclear power as an alternative energy option, it is important to remember that while its carbon output is very low compared to fossil fuels, nuclear fission is still a non-renewable resource.

Coal

A combustible sedimentary rock made up mostly of carbon and hydrocarbon, coal is the most abundantly used fossil fuel worldwide for the generation of electricity. In the United States, approximately 93% of the coal consumed is used to generate electricity (EIA website). The steel, concrete, and paper industries also rely heavily on coal for both heat and byproducts. The combustion of coal results in almost 3 times as many CO2 emissions as the amount of coal combusted - burn a pound of coal, emit almost 3 pounds of carbon dioxide into the atmosphere. Does your state produce coal? Visit the EIA's State Coal Profiles page to find out!

Natural Gas

A natural gas flame
A natural gas flame
Ervins Strauhmanis, Flickr

Natural gas is a gas that is made up mostly of methane and found near other fossil fuels, like coal. Methanogenic processes occurring in landfills and marshes also produce natural gas. Like petroleum, natural gas must first be processed before we can use it as a fuel. It is important to remove most of the other components of natural gas until it is almost purely methane. When combusted, natural gas produces only about half the greenhouse gas emissions as coal does, making it a popular fossil fuel in our increasingly carbon-conscious society. Take a look at these oil- and gas-related maps to learn more about natural gas production and reserves in the United States.

Petroleum

Picture of Sante Fe Rig
Global Sante Fe Rig 140, owned by Transocean
Steven Staiton, Flickr

Petroleum is a toxic, flammable liquid occurring in geologic formations beneath the earth's surface (also known as crude oil). We use oil for a wide variety of things - the largest use of petroleum is for fuel oil and gasoline. But, you'll find petroleum in places you might not expect it as well - pharmaceuticals, plastics, asphalt, kerosene, and synthetic rubber, to name a few. Like natural gas, petroleum must be processed before we can utilize it. Crude oil naturally contains many different types of hydrocarbons, all with different boiling points. So, to process the oil for a specific application, the crude must be heated to a specific temperature range.

Uranium

Picture of Nuclear power plant
A Nuclear power plant
Credit: GeorgiaPower.com

Uranium is a very heavy, fissile metal (U-235) that can be caused to split in a fission chain reaction, producing tremendous quantities of heat which can then be used to generate electricity. Because the reaction of one nucleus capturing another neutron sets off another 2-3 reactions, the resulting chain reaction is exponential and allows us to generate a substantial amount of heat with a relatively small amount of uranium. After extraction, uranium must be processed before we can start the fission process. Most reactors utilize uranium that has been finely ground and then gasified to uranium hexafluoride which is then converted to pellets of uranium dioxide. While nuclear power offers us a greenhouse gas emission-free source of energy, the concerns associated with reactor failure and long-term storage of spent fuel present significant barriers to widespread adoption.

Renewable energy resources

Renewable energy resources are those sources of energy which can be replenished and are not depleted because of our consumption. Renewable resources include wind, solar, geothermal, hydropower, tidal, and biomass energy. Nuclear fusion also falls into this category. Typically, renewable energy resources have much lower greenhouse gas and other emissions associated with use.

But if renewable energy resources are cleaner and offer a sustainable supply of energy, why have we traditionally relied so heavily on non-renewable energy resources like fossil fuels?

  • inexpensive
  • in abundant supply
  • storable

Wind

Please watch the following video:

Energy 101 - Wind Turbines (2:16)

Energy 101 - Wind Turbines
Click here for the video transcript of Energy 101 - Wind Turbines.

We've all seen those creaky old windmills on farms, and they may seem about as low-tech as you can get. Those old windmills are the predecessors of the new modern wind turbines that generate electricity. The same wind that used to pump water for cattle is now turning giant wind turbines to power cities and homes. Ok, have a look at this wind farm in the California desert. a hot dessert next to tall mountains, an ideal place for a lot of wind. Here is another one on the windy prairies of Wyoming. Today's machines are much more complicated than the old prairie windmills, but the principle is the same, both capture the wind's energy. Ok, here is how it works: first, a wind turbine's blade works sort of like an airplane wing, blowing air passes on both sides of the blade. The shape of the blade causes the air pressure to be uneven, higher on one side of the blade, and lower on the other. And that's what makes it spin, the uneven pressure causes the blades to spin around the center of the turbine. On the top, there is a weather vane that is connected to a computer, to keep the turbine turned into the wind so it captures the most energy. Now the blades are attached to a shaft, which only turns about 18 revolutions a minute, and that's not nearly enough to generate electricity by itself. So, the rotor shaft spins a series of gears that increase the rotation up to about 1800 revolutions per minute, and at that speed, a generator can produce a lot of electricity. So, why are wind turbines so tall? Well, the higher up you go, the windier it is. More wind naturally means, more electricity and, in many cases, larger turbines can also capture wind energy more efficiently. Blades can sweep a circle in the sky as large as a football field. Now, what's really cool is that even a small wind farm like this one in Wyoming can generate enough electricity to power more than 9 thousand homes! And larger farms can provide much more clean energy for homes and businesses.

We can put wind to work by utilizing it to power turbines that generate electricity. The blades of the turbines turn a shaft which then powers a series of gears that feed into a generator and produce electricity. Wind turbines can be situated on agricultural or forested land, so there's little or no need to clear new areas of land to site wind fields. Some people take issue with the noise and visual pollution of the wind turbines. There are also concerns about bird and bat mortality. Watch the Wind Turbines video to learn more about how wind energy works.

Solar

solar panels on a sunny day
Solar Panels on a sunny day

Harnessing energy from the sun epitomizes the idea of a renewable energy source. We can use solar energy to heat water or homes and it can be converted into electricity. Currently, converting solar energy to electricity either occurs with the use of photovoltaic cells or solar power plants. The PV cells are able to convert sunlight directly into electricity. Solar power plants use the solar energy to produce steam to operate a generator. Like wind energy, however, solar energy is limited in availability based on localized weather conditions, and it can be challenging to store the energy generated.

Geothermal

a geothermal plant
A geothermal plant

The core of the Earth generates a tremendous amount of heat, and in many places around the world (particularly near tectonically active areas), we can harness that heat in wells and bring it to the surface to heat and cool homes and buildings. Like solar and wind, geothermal power can be captured at an individual level - you install a geothermal heat pump to cool and heat your home - or at a more centralized scale by using dry steam or hot water to generate electricity. Since no fuel is combusted, the plants release no greenhouse gas emissions like a traditional fossil fuel plant would. There are minor emissions of compounds responsible for acid rain.

Biomass

woody biomass
Biomass from fuels reduction on private lands in northeast Oregon

Biomass energy encompasses a broad range of fuels including wood and other plant material, food waste, garbage, and manure. In the case of wood and plant material, it can be processed and combusted for a beneficial end use such as generating electricity or firing a boiler. With food waste and manure, the gases resulting from the processes of decomposition of these materials can be harnessed and combusted for a beneficial end use. Utilizing biomass for energy not only provides us with a renewable energy source but often allows us to put a material that would otherwise be considered waste to a good use. It's important to remember that while a renewable energy source, biomass fuels each have their own set of environmental impacts to consider.

Hydropower

a hydropower plant with a lake in the foreground
A hydropower plant

Water is stored in a reservoir, generating a lot of potential energy. Then it is forced through a dam, turning a turbine, which then turns a generator to produce electricity. Used water is then returned to the river. While much work has been done to ensure that hydroelectric power has minimal negative impact on the environment (including the ability of hydropower facilities to earn a low-impact rating), it is important to recognize the ecosystem disruptions this energy resource can cause. Damming a river and utilizing the water to generate electricity alters the aquatic and riparian ecosystems, can limit the ability of fish to navigate across their natural habitat extent and can change the temperature and composition of the river itself.